2. //package comparable.ex01;
3. 
   
4. import java.util.Arrays;
5. import java.util.ArrayList;
6. 
   
7. //class Testing {
8. 
   
9. //  void main(String[] args) {
10. 
    
11.     Person[] persons = new Person[4];
12. 
    
13.     persons[0] = new Person();
14.     persons[0].setFirstName("Elvis");
15.     persons[0].setLastName("Goodyear");
16.     persons[0].setAge(56);
17. 
    
18.     persons[1] = new Person();
19.     persons[1].setFirstName("Stanley");
20.     persons[1].setLastName("Clark");
21.     persons[1].setAge(8);
22. 
    
23.     persons[2] = new Person();
24.     persons[2].setFirstName("Jane");
25.     persons[2].setLastName("Graff");
26.     persons[2].setAge(16);
27. 
    
28.     persons[3] = new Person();
29.     persons[3].setFirstName("Nancy");
30.     persons[3].setLastName("Goodyear");
31.     persons[3].setAge(69);
32. 
    
33.     for (int i=0; i<4; i++) {
34.       Person person = persons[i];
35.       String lastName = person.getLastName();
36.       String firstName = person.getFirstName();
37.       int age = person.getAge();
38.       println(lastName + ", " + firstName + ". Age:" + age);
39.     }
40. 
    
41.     Arrays.sort(persons);
42. 
    
43.     println();
44. 
    
45.     for (int i=0; i<4; i++) {
46.       Person person = persons[i];
47.       String lastName = person.getLastName();
48.       String firstName = person.getFirstName();
49.       int age = person.getAge();
50.       println(lastName + ", " + firstName + ". Age:" + age);
51.     }
52.  // }
53. //}
54. 
    
55. 
    
56. class Person implements Comparable {
57.   String firstName;
58.   String lastName;
59.   int age;
60. 
    
61.   String getFirstName() {
62.     return firstName;
63.   }
64. 
    
65.   void setFirstName(String firstName) {
66.     this.firstName = firstName;
67.   }
68. 
    
69.   String getLastName() {
70.     return lastName;
71.   }
72. 
    
73.   void setLastName(String lastName) {
74.     this.lastName = lastName;
75.   }
76.   int getAge() {
77.     return age;
78.   }
79.   void setAge(int age) {
80.     this.age = age;
81.   }
82. 
    
83.   int compareTo(Object anotherPerson) throws ClassCastException {
84.     if (!(anotherPerson instanceof Person)) {
85.       throw new ClassCastException(" A Person object expected.");
86.     }  
87.     int anotherPersonAge = ((Person) anotherPerson).getAge();
88.     return this.age - anotherPersonAge;
89.   }
90. }

2. import java.util.Arrays;  
3. import java.util.Comparator;  
4. 
   
5. Song[] songs = new Song[9];
6. 
   
7. void setup(){
8.   int i = 0;
9.  songs[i++] = new Song(2010, 55, 10, 4);
10.  songs[i++] = new Song(2010, 30, 15, 11);
11.  songs[i++] = new Song(2009, 14, 10, 7);
12.  songs[i++] = new Song(2009, 10, 10, 8);
13.  songs[i++] = new Song(2010, 70, 5, 3);
14.  songs[i++] = new Song(2008, 60, 4, 6);
15.  songs[i++] = new Song(2008, 40, 8, 7); 
16.  songs[i++] = new Song(2010, 35, 7, 5); 
17.  songs[i++] = new Song(2009, 20, 7, 4);
18.   //
19.   for(Song song : songs) {
20.     println(song);
21.   }
22.   
23.   Collections.sort(songs, decending(getComparator(YEAR_SORT, WEEK1_SORT)));
24.   
25.   for(Song song : songs) {
26.     println(song);
27.   }
28. }

2. import java.util.Comparator;  
3. 
   
4. public class Song implements Comparable{
5.  int year, week1, ch, high;
6.   
7.  Song(int year, int week1, int ch, int high){
8.    this.year = year;
9.    this.week1 = week1;
10.    this.ch = ch;
11.    this.high = high;
12.  } 
13.  
14.  int getYear(){
15.    return year;
16.  }
17.  
18.  int getWeek1(){
19.    return week1;
20.  }
21.  
22.  
23.  public String toString() {
24.    return year + " - week1 " + week1 + " - ch " + ch + " - high "+high; 
25.  };
26. 
    
27.  // default by year
28.  // Cannot invoke compareTo(int) on the primitive type int
29.  public int compareTo(Object anotherSong) throws ClassCastException {
30.    if (!(anotherSong instanceof Song)){
31.      throw new ClassCastException("A Song object expected.");
32.    }
33.    return ((Song) anotherSong).year - this.year;
34.    };
35. }
36. 
    
37. 
    
38. 
    
39. enum SongComparator implements Comparator<Song> {
40.   YEAR_SORT {
41.     public int compare(Song s1, Song s2) {
42.       return Integer.valueOf(s1.getYear()).compareTo(s2.getYear());
43.     }},
44.    WEEK1_SORT {
45.      public int compare(Song s1, Song s2) {
46.        return s1.getWeek1().compareTo(s2.getWeek1());  
47.      }};
48.   
49.     public static Comparator<Song> decending(final Comparator<Song> other) {
50.       return new Comparator<Song>() {
51.         public int compare(Song s1, Song s2) {
52.           return -1 * other.compare(s1, s2);
53.         }  
54.       };
55.     }
56.     
57.     public static Comparator<Song> getComparator(final SongComparator... multipleOptions) {
58.       return new Comparator<Song>() {
59.         public int compare(Song s1, Song s2) {
60.           for (SongComparator option : multipleOptions) {
61.           int result = option.compare(s1, s2);
62.           if (result != 0){
63.             return result;
64.           }  
65.         }
66.         return 0;
67.       }  
68.     };
69.   } 
70. }
71. 
    
72. 
    
73. // The type Song must implement the inherited abstract method Comparable.compareTo(Object)

2.  public int compareTo(Object anotherSong) throws ClassCastException {
3.    if (!(anotherSong instanceof Song)){
4.      throw new ClassCastException("A Song object expected.");
5.    }
6.    return ((Song) anotherSong).year - this.year;
7.    };
8. }

  // Cannot find anything named "YEAR_SORT"

  //Collections.sort(songs, decending(getComparator(YEAR_SORT, WEEK1_SORT)));

  // The function getComparator(SongComparator, SongComparator) does not exist.

  //Collections.sort(songs, decending(getComparator(SongComparator.YEAR_SORT, SongComparator.WEEK1_SORT)));

  // Cannot find anything named "Song.SongComparator"

  //Collections.sort(songs, decending(getComparator(Song.SongComparator.YEAR_SORT, Song.SongComparator.WEEK1_SORT)));

  // The function decending(SongComparator, SongComparator) does not exist.

  //Collections.sort(songs, getComparator(decending (SongComparator.YEAR_SORT, SongComparator.WEEK1_SORT))); 

You removed compareTo without removing the implements Comparable part, right? 

2. import java.util.Arrays;  
3. import java.util.Comparator;  
4. 
   
5. Song[] songs = new Song[9];
6. 
   
7. void setup(){
8.   int i = 0;
9.  songs[i++] = new Song(2010, 55, 10, 4);
10.  songs[i++] = new Song(2010, 30, 15, 11);
11.  songs[i++] = new Song(2009, 14, 10, 7);
12.  songs[i++] = new Song(2009, 10, 10, 8);
13.  songs[i++] = new Song(2010, 70, 5, 3);
14.  songs[i++] = new Song(2008, 60, 4, 6);
15.  songs[i++] = new Song(2008, 40, 8, 7); 
16.  songs[i++] = new Song(2010, 35, 7, 5); 
17.  songs[i++] = new Song(2009, 20, 7, 4);
18.   //
19.   for(Song song : songs) {
20.     println(song);
21.   }
22.   // Cannot find anything named "YEAR_SORT"
23.   //Collections.sort(songs, decending(getComparator(YEAR_SORT, WEEK1_SORT)));
24.   // The function getComparator(SongComparator, SongComparator) does not exist.
25.   //Collections.sort(songs, decending(getComparator(SongComparator.YEAR_SORT, SongComparator.WEEK1_SORT)));
26.   // Cannot find anything named "Song.SongComparator"
27.   //Collections.sort(songs, decending(getComparator(Song.SongComparator.YEAR_SORT, Song.SongComparator.WEEK1_SORT)));
28.   // The function decending(SongComparator, SongComparator) does not exist.
29.   //Collections.sort(songs, getComparator(decending (SongComparator.YEAR_SORT, SongComparator.WEEK1_SORT)));
30.   // Cannot find anything named "SongComparator"
31.   Collections.sort(songs, SongComparator.decending(SongComparator.getComparator(SongComparator.YEAR_SORT, SongComparator.WEEK1_SORT)));
32.   
33.   for(Song song : songs) {
34.     println(song);
35.   }
36. }

2. import java.util.Comparator;  
3. 
   
4. public class Song implements Comparable{
5.  int year, week1, ch, high;
6.   
7.  Song(int year, int week1, int ch, int high){
8.    this.year = year;
9.    this.week1 = week1;
10.    this.ch = ch;
11.    this.high = high;
12.  } 
13.  
14.  int getYear(){
15.    return year;
16.  }
17.  
18.  int getWeek1(){
19.    return week1;
20.  }
21.  
22.  
23.  public String toString() {
24.    return year + " - week1 " + week1 + " - ch " + ch + " - high "+high; 
25.  };
26.  
27. // The type Song must implement the inherited abstract method Comparable.compareTo(Object)
28. 
    
29. /*
30.  // default by year
31.  // Cannot invoke compareTo(int) on the primitive type int
32.  public int compareTo(Object anotherSong) throws ClassCastException {
33.    if (!(anotherSong instanceof Song)){
34.      throw new ClassCastException("A Song object expected.");
35.    }
36.    return ((Song) anotherSong).year - this.year;
37.    };
38. }
39. */
40. 
    
41. 
    
42. 
    
43. enum SongComparator implements Comparator<Song> {
44.   YEAR_SORT {
45.     public int compare(Song s1, Song s2) {
46.       return Integer.valueOf(s1.getYear()).compareTo(s2.getYear());
47.     }},
48.    WEEK1_SORT {
49.      public int compare(Song s1, Song s2) {
50.        //return s1.getWeek1().compareTo(s2.getWeek1());  
51.        return s1.week1 - s2.week1;
52.      }};
53.   
54.     public static Comparator<Song> decending(final Comparator<Song> other) {
55.       return new Comparator<Song>() {
56.         public int compare(Song s1, Song s2) {
57.           return -1 * other.compare(s1, s2);
58.         }  
59.       };
60.     }
61.     
62.     public static Comparator<Song> getComparator(final SongComparator... multipleOptions) {
63.       return new Comparator<Song>() {
64.         public int compare(Song s1, Song s2) {
65.           for (SongComparator option : multipleOptions) {
66.           int result = option.compare(s1, s2);
67.           if (result != 0){
68.             return result;
69.           }  
70.         }
71.         return 0;
72.       }  
73.     };
74.   } 
75. }